I wasn’t a good student when I was younger, but when I found what I wanted to do (anthropology), I started getting straight As and even went on to get a PhD.
I think that there’s a few things to consider: ADHD is a spectrum disorder, which means that not only are the effects different for different people, but the degree to which they are affected is different too.
People with ADHD often concentrate well on what they are interested in. If you liked learning or were interested in the content of your classes, or liked the reward system well enough that you wanted to do well for the As/kudos/whathaveyou, then having ADHD and being a good student could go together.
If the difficulties you listed interfere with your life, then asking to be assessed for ADHD makes sense, whether or not you were a good student!